学习资料：开涛的《跟我学SpringMVC.pdf》
众所周知，springMVC是比较常用的web框架，通常整合spring使用。这里抛开spring，单纯的对springMVC做一下总结。
概念
HandlerMapping：处理器映射，对请求的URL进行映射为具体的处理器（如果有拦截器也包含拦截器，会将Handler和多个HandlerInterceptor封装为HandlerExecutionChain对象）
HandlerAdapter：处理器适配器，适配不同类型的处理器，如Controller、AbstractController等
Handler：处理器，即开发的Controller
ModeAndView：模型和视图，未来会渲染为具体的视图
ViewResolver：视图解析器，将逻辑视图名称转化为物理视图
View：视图
流程图
源码简析（摘自DispatcherServlet源码部分）
由于springMVC的配置本身就上一个servlet，所以跟踪代码doService()=>doDispatcher()，核心代码如下所示，中文注释自己加的
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
//对文件上传类型的数据进行处理，使用MultipartResolver解析
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
//使用HandlerMapping进行映射，将一个Handler和多个HandlerInterceptor封装为HandlerExecutionChain对象
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}
//根据Handler获取合适的Handler适配器
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (logger.isDebugEnabled()) {
logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
/*
* 调用拦截器的preHandle()，返回true继续执行下一个拦截器或处理器，返回false中断流程并执行执行成功的拦截器的afterCompletion()。
*/
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
//使用HandlerAdapter执行Handler并返回ModeAndView
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
//调用拦截器的postHandle()方法
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
//处理转发结果，包含ModeAndView的视图解析，视图解析后调用拦截器的afterCompletion()函数
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}